PREHEAT oven to 350° Whisk together whole eggs, egg whites, and sour cream in a large bowl. Add thyme, basil, oregano, black pepper, and salt and beat so that there are no clumps of spices.
HEAT the olive oil over medium heat in a large oven-safe skillet. Add the garlic and cook for about 30 seconds, until it begins to lightly brown. Add the onion and asparagus. Cook for 5 minutes or until onion begins to brown and asparagus is almost tender. Add additional oil to the pan, if needed, and toss in the greens. Continue to cook, stirring frequently, until the greens are cooked down, about 3 to 5 minutes.
SPREAD the vegetables evenly in the skillet. Pour the egg mixture over the vegetables, ensuring everything is dispersed evenly throughout the skillet. Sprinkle with feta cheese.
PLACE the skillet in the oven and bake until the sides are golden brown and the eggs no longer run when pierced with a fork, about 25 to 35 minutes.